For more than a year, as advocates and activists have worked to build public support for traffic diverters on Southeast Clinton Street, a question has hovered: are car volumes really worse than they used to be?

The freshly gathered data seems likely to bolster the case for diverters on Clinton Street that could reduce cut-through auto traffic on the important bikeway, especially once it becomes the main runway to the new Tilikum Crossing bridge in September.

In spring of 2014, the city measured 268 westbound cars during the morning rush hour on SE Clinton at 25th, a 66 percent increase over the 2008 level. But because that was in the middle of road work and construction on nearby Division Street, some said Clinton’s auto traffic might return to “normal” once Division’s new streetscape was finished.

According to traffic counts released by the city Tuesday morning, it hasn’t.

Westbound peak-hour auto traffic on Clinton near 25th remains 55 percent higher than it was in 2008. Eastbound traffic during the evening rush hour, by contrast, is up just 16 percent.

The new counts were conducted on Tuesday, June 9, a few days before the end of the Portland Public Schools trimester. The same data showed that traffic volumes on Clinton west of 30th Avenue are also among the highest in the neighborhood greenway system, carrying 129 westbound cars during the morning peak hour and 143 eastbound cars during the evening peak, for a total of 2,335 cars in both directions for the full day.

The national standard for neighborhood greenways — intended to be a citywide grid of low-stress, all-ages bikeways that build a long-term constituency for better biking — is to keep traffic volumes below 1,500 cars per day.

The freshly gathered data seems likely to bolster the case for diverters on Clinton Street that could reduce cut-through auto traffic on the important bikeway, especially once it becomes the main runway to the new Tilikum Crossing bridge in September.

But the data also raises new questions. What on earth is going on here? Why would more people be driving on Clinton in one direction but not in the other?

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Fortunately, a team of volunteer biking advocates is already on the case. With support from Kari Schlosshauer and other members of the neighborhood group Safer Clinton, local transportation analyst Brian Davis (of Lancaster Engineering but working on his own time) led a squad of volunteers on June 2 to capture some of the richest data that’s ever been gathered about inner Southeast Clinton traffic patterns, including traffic volumes and turning movements from 7:35 to 8:35 a.m. and 4:40 to 5:40 p.m.

Based on their numbers, here’s a rough image that captures the phenomenon Davis thinks is happening:

Arrows are not to scale.(Graphic: BikePortland)

“The problem gets worse heading west; Clinton seems to be ‘collecting’ the excess traffic from Division as you get closer to the central city,” Davis said in an email. “This is a phenomenon that doesn’t really have an evening equivalent, so we’re seeing lower volumes here. They’re still high, but not disproportionate to daily traffic.”

That combination of diverters, Davis thinks, would reduce cut-through car traffic without interfering with local trips or the route of TriMet’s No. 10 bus.

Portland Bicycle Planning Coordinator Roger Geller, who coordinated the collection of fresh traffic data on Clinton, said the city is preparing to gather more information that will also be useful in understanding the area: the number of cars using Division Street each hour.

PBOT is currently analyzing Clinton and they are likely to install some mix of speed bumps, signage and diverters by the end of summer.

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67 Comments

rickJuly 8, 2015 at 10:32 am

Why not make a chicane that has a street tree? Something like a swale instead of speed bumps?

Surly you must have noticed what happens to median trees and “refuge” trees. They do not last a year. Even the average age of urban street trees is only about 15 years. Trees are poor choices for traffic control devices. Couple that with a chicane (see GIF in other post) and you are throwing away good money and killing trees.

I could just as easily post a link to the refuge median at Foster and Springwater Trail. Any tree planted would be Max. 2″ caliper, not the 10″ caliper tree that is Google referenced. 2″ caliper trees make great sport for “roll’n coal” duallys.

Still feels like a lot of “more study”. We have this and other data already. Put the diverters in, then run a couple more counts to compare traffic counts. Wasn’t that the whole point of experimental? Progress with no progress.

I think it’s more likely that it’s easier to make a frustrated right turn off of Powell in the morning than it is to get to Clinton when heading back to Gresham from downtown. Westbound, you have to plan for it. Eastbound you just have to make a quick turn out of the congestion and into the neighborhood.

I’m confused by the disconnect between the direction of the arrows (northbound) and Brian’s comments about Clinton collecting overflow from Division. It seems to be (and the arrows indicate) car traffic overflowing from Powell, not Division. That jibes with my observation that Powell backs up in the a.m. from the RIB to the 30s, with Clinton being a popular shortcut. Traffic was much worse in the 2015 school year than 2014, so your spike in 2014 was probably from Division construction, but the 2015 high number is probably Powell.

Basically, the greenway is pretty comfortable until you get west of 34th. Between 33rd & 28th, you see a lot of cars entering the greenway from Division Street, presumably to avoid a congested corridor that begins with the signal at Division/26th. At 26th, 21st, and 17th, though, we are seeing a lot of cars entering Clinton by making northbound lefts——this is indeed Powell traffic.

So I think you’re getting a little bit of both. West of 26th, it’s primarily diverting from Powell and east of 26th it’s primarily from Division.

Thanks, Brian. It’s good to be looking at the 17th Avenue diverter now, before the storm. Most a.m. Clinton bike traffic peels off to go to north through Ladd’s, because the Clinton-to-the-river signal timing is so bad. But when the new bridge opens, west of 21st Avenue is going to be a huge bike route (even with the bad signals and interesting routing).

Yup. And I was surprised to see that the heaviest auto volumes were actually west of 17th during both peaks. I would have guessed that they were between 21st and 26th. So it’s best to nip this in the bud.

17th would also do a ton to solve the evening problems, since we’re seeing that most eastbound auto traffic enters Clinton at 12th and stays on clear to 39th. Diversion here would stop that problem before it starts. I am on the fence about whether a straight median diverter or a SW-NE diverter would work better here, though. The former would better address evening problems, whereas the latter would better address morning ones.

By “interesting routing” do you mean confusing fluster cluck of turns, rail crossings and bus bus route conflicts? I wonder how well embraced the Clinton to Tillicum route will be after a few commutes with a 10 minute wait for a freight train crossing?

That was my being diplomatic, yes. And I harbor no ill will toward freight trains. Yes, it’s annoying, but occasional. But when there are no trains, it could be a lot better. I’m not sure exactly how. I expect that, as more people ride that way, there will be more people getting fed up and running lights, getting creative. And hopefully we figure out some serious changes before we start getting all sorts of crashes. There’s one tight blind turn where bikes go wide into oncoming bikes, there’s the stop sign that no one heeds that will soon feature buses, there’s … well, you know what it’s like.

The whole signal system at the SE 11th-12th Ave / RR-Max crossing is seriously in need of adjustment. There is too much time in each cycle where all traffic is stopped in every direction for all modes (bikes/cars/peds). Creates unnecessary frustration for all users and encourages “innovation” from otherwise law abiding travelers.

In 2010, the Bicycle Transportation Alliance and Portland Bicycle Advisory Committee were concerned that traffic volumes on Clinton were too high and that the Division project would only make it worse. We managed to get the following language added to the Division Streetscape plan:

“If PBOT determines that diversion has occurred as a direct result of traffic changes on Division Street, staff will take measures to prevent any further diversion. Staff will work with the community and residents on Clinton to examine additional traffic calming devices or passive/active diversion measures on Clinton Street (SE 12th to 39th).”

28th Avenue. The goal of that diverter is to eliminate the utility of Clinton for WB cut through traffic from Division, which begins to enter the Greenway in the early 30’s to avoid congestion starting at the 26th/Division signal.

The left-turn prohibition would be paint/signage, and would be part of a larger plaza treatment at 26th & Clinton that I believe some other SaferClinton folks are working up some drawings for. It would only be at this intersection. We observed that most of the vehicles entering Clinton there are staying on Clinton all the way to 12th, so that gives me hope that diversion onto parallel neighborhood streets would be kept to a minimum. Getting from 26th to 12th without using Clinton would be a meandering route with a lot of stops, especially with a diverter present at 17th, that wouldn’t really offer a travel time benefit over fighting traffic on Powell.

Signed turn prohibitions need constant enforcement to be truly effective and also could be argued against by businesses – ‘you’re cutting off half the cars that drive by…’ Internal diversion – away from the commercial land uses – would be much more doable.

I agree, the best way to address that northbound left-turning traffic from 26th would be with a diverter west of 26th. The problem is that we have to allow for passage of the #10 bus in both directions, or else get Tri-Met to agree to re-route it, which is a possibility folks are actively exploring. The latter possibility would certainly be preferable, but it’s certainly not imminent at this point.

It’d need to be part of that larger plaza treatment to be an effective solution. But if we can mostly eliminate the westbound through movements via diversion at 28th, volumes west of 26th would be approaching the ideal range even if you don’t get perfect compliance there.

For cyclist safety wouldn’t 29th 0r 30th be better? I’m thinking as close to the top of the hill as possible. This way potential bicycle collisions with the infrastructure occur at slower travel speeds – say 12-15 mph instead of 20+mph.

Plaza treatment at 26th and Clinton would be great. The North-South portion of this intersection along 26th is really no good – the bike lanes simply disappear into parked cars. I have to jockey with same-direction car traffic as the bike lane ends every time I ride here. Many cars simply speed up to get in front of me as the pinch approaches. Not sure local business will want to support any type of car diet for this area, need to figure out how to convince them most of there customers are not driving around here, anyway. No left-turn for autos onto Clinton would be pretty awesome.

“need to figure out how to convince them most of there customers are not driving around here.”

Excellent point! Coming up with some kind of stats for that would be wondrous. I live on 26th near Clinton and it is through traffic I see–lots and lots of it. Next to nobody’s stopping and shopping and eating. Also agree about the 10 being rerouted. That’s my bus and it’s always delayed by squeezing along that Clinton/21st route–can barely make that pinchy turn at 21st.

The idea of “a left-turn prohibition, excepting bikes and buses, northbound on 26th” makes me giddy in general. My next request would be giant, obstructive traffic calming measures on 26th, but I know it’s a designated emergency corridor (unhappy sigh).

You can use Google Maps/Waze to find recommended driving directions for a typical weekday morning. If you input your origin as somewhere on Powell between SE 39th and SE 17th, and your destination as SE 12th Northbound (north of Division), it looks like Google/Waze will typically divert you onto Clinton as the preferred east-west connection to SE 12th. Try it and see for yourself.

Not sure what you are getting at. Westbound on SE Clinton has only one direction for a car to get to, currently, which is North on 12th Ave. They put in a nice green stripe to allow cars to turn right / north off clinton and bikes to go straight west into the rail crossing mess, eliminating this right hook a few months ago.

Thanks for the analysis and observations. On my frequent Clinton rides, I also notice quite a few cars between 12th and 21st and was wondering what the thought was behind proposing a median diverter at 17th, versus maybe doing dual partial closure diverters: one that blocks eastbound motorists at 12th, and another that blocks westbound motorists at either 17th or even 21st?

I think that’s certainly another viable option. My only concern with that would be the die-hard cut through drivers could loop around the EB ‘exit only’ at 12th using Ivon, and without the diverter at 17th they could continue all the way to 28th.

I think a WB ‘exit only’ diverter on 17th functionally accomplishes the same thing for morning traffic (cuts off the NB lefts) as a median diverter, but doesn’t help much for evening traffic. Moving it to 21st addresses the Powell cut through traffic entering Clinton there, but leaves the traffic entering at 17th unchecked.

Combining the treatments is an intriguing option. If you left the median diverter at 17th and added exit only’s to restrict eastbound traffic at 12th and westbound traffic at 21st, that would robustly solve pretty much every problem we’re seeing. The question then becomes how many treatments the city has the appetite for, and how much pushback you’d get from businesses around 21st.

Arterial roads were designed for a specific reason: to keep traffic off of side streets. When you reduce capacity on arterial roads, where are the cars going to go? The drivers are not suddenly going to abandon their cars and start biking. When you have a grid system, they are simply going to shift over to the side streets.

This will be an unwinnable game of wack-a-mole for years to come. The same thing is going to happen on NE Broadway and Tillamook. You can bet on it.

Tillamook is not nearly so navigable. But yes, this is current reality. I’m more for neutralizing all streets inside of a determined border where traffic starts to funnel. Lower speed limits all the way around. Drivers gain 5 mins of morning news or music and a day’s worth of less stress. The hurry-up-and-stress approach to society is only serving publishers of self-help books and big pharm.

The issue is speed. I would rather see reduced speed limits on the arterial roads with more speed cameras on those roads. Reducing capacity on arterial roads will result in more volume/crashes/problems on previously quiet side streets. This isn’t rocket science.

The rule of thumb, outside of areas like downtown, is 1,000 vehicles per hour in the peak hour per lane. Capacity is not necessarily number of lanes x the standard. when there is no center lane for left turning vehicles to use, they have to stop in that inside lane. During rush hour, this practically eliminates that lane from the capacity equation. When a road diet is possible, current capacity is usually not affected, while safety is improved. It is future capacity that may be sacrificed when a road diet is implemented, though I’ve heard there may be fewer cars in the future 😉

M, It’s not rocket science, but it is a science (and art) and it’s also not so simple. Many roads were constructed in the past using different assumptions about what the future would look like. That past vision of the future looks less and less likely, or desirable. I would not be surprised if many modern cities move many more people using many fewer private automobiles in many places in the world (including the US) than in Portland.

I discovered this when trying to cut through Berkeley, CA… they have so many diverters that you eventually give up because you either become lost or spend lots of time only to end up on a main road anyway…

Tri-Met’s No 10 bus: this needs to be routed off of Clinton. It uses Clinton for 5 blocks, between 26th and 21st, and totally parallels Division. This bus route needs to be re-routed to SE Division. With the old school traffic calming islands on this section, it is obvious the bus has a very hard time making these turns and also the right turn on 21st from Clinton. It is not fun riding on Clinton with a bus bearing down right behind you on this section.

the bus route was there before the ‘greenway’ designation. see my comments further down regarding geometry. the bus on Lincoln, 52nd to 60th is the same issue. The south to west turn at 60th/Division is too problematic and expensive to fix (and some residents on Lincoln like the bus route near by).

Having single lane traffic on Division with no cut-ins for the no: 4 bus is also a problem. Cars get backed up too easily, and then they look for alternative routes. i) there need to be cut-ins at bus-stops. ii) there do not need to be bus-stops every other block, each of which is short. Get rid of every other Bus stop. As an aside, why the hell are there 2 bus-stops on one block outside Cleveland High School on Westbound Powell !!

Existing road design was the reason they used Clinton in the past (20th to 26th) – the SW corner at Division/26th was too restrictive. Not sure if this has (Division project)/will change with the 20’s project. Clinton where the bus runs has the longer (=faster) speed tables, instead of speed bumps (past practice).

Here’s the elephant in the room: it’s new development that’s been completed without accommodation for parking.

I ride Clinton most afternoons, following the bike boulevard from 12th to 82nd. I can’t tell you how many drivers seem to be circling, looking for parking, eager to get a block up or a block over to find a place to stash their car while they dine at the food cart pod, D Street Noshery or Bollywood Theater, etc. And that’s not even bringing up the fact that multiple new condo / apartment complexes have arrived on Division without parking– yet the residents still park.

The “low car lifestyle” is a lie. A big, fat, hairy lie told by developers eager to find loopholes to cut corners in a hot real estate market and suck tax breaks off our city. They have no long term stake in our neighborhoods, but our city government doesn’t seem to mind that they’re building a generic luxury playground for a demographic that almost universally owns cars– regardless of the greenwashed nonsense that their development’s brochure promises.

These people park on the streets daily and will continue to do so until we find a real, viable parking solution for neighborhoods that have been recently bulldozed, built out-of-scale and then re-sold at insane prices to speculators and transplants. Until we meet the demand of the insincere lifestyle tourist set– not that we want to, but because we now have to– expect stress, injury and malady. It’s an expense borne on the backs of bike commuters all across our city, yet the loudest pro-bike voices remain militantly unaware, playing the pied pipe song of “density” to help shuffle long-time residents and minorities out to the suburbs. Who– and what– are you really advocating for?

It is not a lie; it just takes time to manifest itself. We’re building for 30-80 years. Well before then we’ll have no cars, and will thank the foresight of our leaders for doing what little they did to anticipate this.